Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$167.32	7.224%	$179.4072	$179.41	$179.40	$179.40
Purchase #2	$102.72	13.549%	$116.6375	$116.64	$116.65	$116.60
Purchase #3	$146.67	3.128%	$151.2578	$151.26	$151.25	$151.30
Purchase #4	$185.61	13.132%	$209.9843	$209.98	$210.00	$210.00
Purchase #5	$46.37	8.417%	$50.273	$50.27	$50.25	$50.30
Purchase #6	$95.52	3.393%	$98.761	$98.76	$98.75	$98.80
Purchase #7	$83.70	10.255%	$92.2834	$92.28	$92.30	$92.30
7 purchase totals =	$827.91		$898.6042	$898.60	$898.60	$898.70